A STELLAR VOYAGE
Explore The Solar System With 15 Fascinating Cosmic Destinations!
Published on February 7, 2024
Since time immemorial, humanity has been fascinated by the vastness of the sky and the mysteries that lie beyond. This fascination bore countless stories, myths, and theories aiming to explain our place in the larger universe.
In this article, we will take a tour within the boundaries of our solar system . Join us on a journey of discovery through 15 celestial objects in our cosmic neighborhood and uncover some of the captivating stories behind them.
Credit: Maciek Sulkowski
The leader of the pack. It's the stellar centerpiece and namesake of the solar system, and it has inspired various myths in many cultures throughout human history. The Ancient Greeks, for example, believed that the god Helios drove a fiery chariot across the sky, thus explaining the apparent motion of the Sun from east to west.
The Sun is _massive_—it contains approximately 99.85% of the mass of the entire solar system. That is 333,000 times the mass of the Earth or 1047 times the mass of Jupiter, the largest of the planets and the second most massive object in the system.
Mercury is the closest planet to the Sun and, since Pluto was reclassified as a dwarf planet in 2006, it is also the smallest planet in the solar system. It is barely larger than Earth's natural satellite, the Moon.
Named after the Roman messenger of the gods, Mercury does a lot to earn its name: it revolves around the Sun once every 88 Earth days, completing its orbit faster than any other planet.
Credit: Planet Volumes
Venus is often referred to as Earth's twin planet because they are very similar in size and composition. However, we wouldn't recommend it as a vacation spot: Due to its incredibly dense atmosphere, Venus' mean surface temperature is close to 876°F.
Venus is a quirky planet—alongside Uranus, they are the only two planets that rotate clockwise on their axes. From the surface, the Sun would appear to rise from the west and set on the east. In addition, Venus moves around the Sun faster than it rotates on itself. That would make a year on Venus shorter than a day.
Humanity's cradle and home and, so far, the only planet known to support life. Slightly larger than Venus, Earth is the largest of the inner planets—the four rocky planets on this side of the asteroid belt. Beyond the belt, in the outer solar system, roam the gas and ice giants.
Curiously, Earth is the only planet whose English name does not come from the name of a Roman or Greek deity. Instead, it has Old English roots, and it simply means "the ground."
Earth's only natural satellite, a bright and familiar face in the night sky. As culturally significant as the Sun throughout humanity's history, its influence on life on Earth is undeniable and plain for all to see.
Our Moon is the fifth largest moon in the solar system. While it's close by in astronomical terms, it's still quite far—it sits a surprising 238,855 miles away from Earth. Thirty Earth-sized planets would fit in the distance between us and our closest celestial companion.
Credit: Planet Volumes
The fourth planet from the Sun is easily recognizable in the night sky—it shines brightly and with a distinctly red coloration. This has earned Mars its nickname, "the Red Planet," a moniker fitting for a planet named after the Roman god of war.
Mars is one of the five planets—Mercury, Venus, Mars, Jupiter, and Saturn—that are visible to the naked eye. Ancient astronomers could tell them apart because of their constant movement against the sea of stars. That's the reason why the Ancient Greeks called these celestial objects planetes , meaning "wanderer."
Separating the inner and the outer solar system you'll find the asteroid belt. This region is brimming with relatively small objects—much smaller than planets—called asteroids. It's been estimated that about 60% of the belt's total mass is contained within its four largest objects: Ceres, Vesta, Pallas, and Hygiea.
Ceres is, by some margin, the largest object in the asteroid belt. When it was first discovered in 1801, it was announced as a new planet. However, when more and more similar objects were discovered in the region, Ceres' classification was revised to that of an asteroid, and it ultimately became a dwarf planet in 2006.
Credit: Planet Volumes
Beyond the belt we step into a realm of giants, and Jupiter is chief among them. The second most massive object in the solar system—after the Sun itself—Jupiter is so large that it contains more than twice the mass of all the other planets combined. The entire circumference of the Earth would fit snugly on top of Jupiter's iconic Great Red Spot.
Jupiter is a gas giant and its stormy atmosphere, made primarily of hydrogen and helium, has been probed by automated spacecraft since NASA's Pioneer 10 approach in 1973. Since then, NASA has kept sending missions to Jupiter's region, and upcoming missions are scheduled for the future.
Credit: Kevin Gill from Nashua, NH, United States, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons
We'll stay in Jupiter's neighborhood for a quick stop on Europa. Alongside Io, Ganymede, and Callisto, Europa is part of a select group called the Galilean moons. They are the largest of the more than 90 known moons of Jupiter.
The four Galilean moons are named in honor of Galileo Galilei , who first spotted them in 1610 with his homemade telescope. Nowadays, if you know where to look, they can be easily spotted with nothing but a pair of binoculars.
Europa has an icy surface that could hide a vast saltwater ocean beneath. According to NASA, this might make it a promising candidate as a place capable of supporting life beyond Earth.
Saturn is not the only planet to sport rings—all of the outer giants have them. It's a natural consequence of their size. However, none of them are so spectacular.
Saturn is the farthest and dimmest planet that can be seen in the night sky with the unaided eye. As such, it's the last one that humanity has known of since ancient times. It is named after the Roman god of time and agriculture.
The rings were first observed—you might have guessed it—by Galileo Galilei in 1610, but he was unable to identify them as such: He described them as Saturn's "ears." It wasn't until 1655 that Christiaan Huygens first described them as a disc surrounding the planet.
Credit: NASA/JPL-Caltech, Public domain, via Wikimedia Commons
Saturn's largest moon is only slightly smaller than Ganymede—Jupiter's largest moon—but it's still larger than the planet Mercury. On top of that, it's the only moon known to sustain a sizable atmosphere, and its icy crust is riddled with flowing rivers. However, instead of water, the rivers and seas on Titan's surface are primarily made up of methane and ethane.
Like Europa, Titan hides its water underneath a frozen shell—a vast subsurface ocean waiting to be explored. Who knows what mysteries lie beneath?
Credit: Planet Volumes
Uranus is a planetary oddball. Besides sharing Venus' retrograde rotation, its axis is so tilted that it appears to be spinning on its side. It's a very cold and windy planet, with winds that can reach up to 560 miles per hour.
Uranus and Neptune are classified as ice giants. Their size and composition differ vastly from that of Jupiter and Saturn, the gas giants. They are sizeably smaller, and they have much higher concentrations of water, ammonia, and methane. Astrophysicists call these substances _ices_—hence the name.
We're approaching the end of our voyage, and we've finally reached the 8th and most distant planet in the solar system. The story of its discovery is unique among planets: Neptune's presence was mathematically predicted after observing unexplained disturbances in Uranus' orbit. Based on those predictions, Neptune was first observed in 1846 by astronomer Johann Galle.
The second of the ice giants, Neptune is a little smaller in volume than Uranus. However, it is also denser, and therefore slightly more massive. Its iconic blue color comes from traces of methane present in its atmosphere.
A small rocky world on the outskirts of our cosmic neighborhood. Long considered to be the solar system's ninth planet, Pluto's demotion to dwarf planet in 2006 caused ripples both in and out of the scientific community. Pluto sits in a region called the Kuiper Belt, a disc similar to the asteroid belt that encircles the outer solar system.
Pluto's classification history mirrors that of Ceres: as more and more objects of similar characteristics were found in the Kuiper Belt, scientists were forced to either accept them all as planets or to change the very definition of planet . They chose the latter and, sadly, Pluto just missed the criteria.
Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute, Public domain, via Wikimedia Commons
Pluto is named after the Roman god of the underworld. It's only fitting that Charon, its largest moon, shares its name with the ferryman who carried the souls of the dead to the afterlife in Greek and Roman mythology.
Charon is uncharacteristically large for a moon: it has half the diameter and ⅛ of the mass of Pluto. On top of that, Charon and Pluto are mutually tidally locked, meaning that they always show each other the same face. Because of this unusual relationship, it's been argued that Pluto and Charon should be treated as a binary dwarf planet system.